Upright vacuum cleaners which are convertible for cleaning surfaces above a floor surface (i.e., above-the-floor cleaning) are well know in the prior art. For example, U.S. Pat. No. 2,898,621 discloses a conversion arrangement for an upright vacuum cleaner. Typically, and as is taught by U.S. Pat. No. 2,898,621, the suction hose permitting conversion extends from the nozzle assembly, around the periphery of the vacuum cleaner housing, to the canister assembly which houses the dust bag. Such an arrangement is disadvantageous because the suction hose can easily become caught on, or entangled in, various surfaces when the vacuum cleaner is manipulated for floor cleaning.
Similarly, U.S. Pat. No. 4,761,850 discloses an upright vacuum cleaner convertible for above-the-floor cleaning with an integral tool storage compartment. Again, the suction hose is disadvantageously arranged because it extends well beyond the periphery of the vacuum cleaner housing.
When operating a convertible upright vacuum cleaner as an above-the-floor vacuum cleaner, it is advantageous to disengage the agitator brush to prevent possible damage to a floor surface that might occur while the vacuum cleaner remains stationary for a prolonged period of time. U.S. Pat. No. 2,502,674 discloses an arrangement whereby an electrical switch responsive to the insertion of a tool for converting the vacuum cleaner for above-the-floor cleaning causes a clutch to disengage the agitator brush upon insertion of the tool. Such an arrangement is complex and costly, requiring numerous additional components in the construction of the agitator brush.
U.S. Pat. No. 2,218,180 discloses an upright vacuum cleaner wherein the agitator brush is oscillated back and forth by an electrical vibrator. A switch responsive to the insertion of a tool used to convert the vacuum cleaner for above-the-floor cleaning causes an open condition in the electrical circuit to the vibrator. This arrangement is disadvantageous because it requires a separate converter tool for above-the-floor cleaning and because a vibration type agitator brush is not effective in loosening dirt embedded in a carpeted surface.
In addition to being able to disengage the agitator brush when operating a convertible upright vacuum cleaner as an above-the-floor vacuum cleaner, it is also advantageous to disengage the agitator brush when cleaning bare floor surfaces to prevent possible scratching. U.S. Pat. No. 3,291,418 discloses a mechanism for sensing the presence of a bare floor surface. A pressure sensing switch mounted within the nozzle housing in proximity to the agitator brush closes the electrical circuit to the agitator motor when a preselected vacuum level is achieved. The vacuum level generated in the nozzle differs depending on the floor surface being cleaned (i.e., a carpeted surface as opposed to bare floors) because a carpeted surface prevents air leaks around the mouth of the nozzle that would otherwise be present when cleaning a bare floor surface. This arrangement is very complex and is not reliable for all surfaces.